1. Field of the Invention
The present invention relates to an air conditioner comprising a plurality of compressors, and more particularly to a method for operating compressors of an air conditioner in which the plural compressors are sequentially operated when a cooling or heating load in a room is in the highest grade.
2. Description of the Related Art
Generally, an air conditioner is an appliance for cooling or heating a room using a refrigerating cycle of a refrigerant compressed by compressors.
The compressor includes a compression unit provided with a compression chamber for compressing the refrigerant, and a motor unit for variably changing the capacity of the compression chamber. In order to meet a trend towards large scale and multi-function applications, the air conditioner has been developed to comprise two compressors or an inverter-type compressor so that the total operating capacity of the compressors can be variably changed in accordance with a cooling or heating load in a room, thereby reducing a power consumption rate required to operate the compressors.
FIG. 1 is a schematic view of a conventional air conditioner provided with two compressors, which is operated in a cooling mode. FIG. 2 is a schematic view of the conventional air conditioner provided with two compressors, which is operated in a heating mode.
As shown in FIGS. 1 and 2, the conventional air conditioner comprises first and second indoor heat exchangers 2 and 12 for heat-exchanging a refrigerant with air in a room, thereby cooling or heating the room, first and second outdoor heat exchangers 4 and 14 serving as condensers for condensing the refrigerant in case that the first and second indoor heat exchangers 2 and 12 function as coolers, while serving as evaporators for evaporating the refrigerant in case that the first and second indoor heat exchangers 2 and 12 function as heaters, first and second compressors 6 and 16 for compressing the refrigerant from a low-temperature and low-pressure gaseous state into a high-temperature and high-pressure gaseous state in order to supply the high-temperature and high-pressure gaseous refrigerant to the first and second indoor heat exchangers 2 and 12 or the first and second outdoor heat exchangers 4 and 14, a first expansion device 8 arranged between the first indoor heat exchanger 2 and the first outdoor heat exchanger 4 to expand the refrigerant into a low-temperature and low-pressure state, a second expansion device 18 arranged between the second indoor heat exchanger 12 and the second outdoor heat exchanger 14 to expand the refrigerant into a low-temperature and low-pressure state, and a control unit (not shown) for controlling operation of the first and second compressors 6 and 16. The first indoor heat exchanger 2, the first compressor 6, the first outdoor heat exchanger 4 and the first expansion device 8 are connected by a first refrigerant pipe 9, and the second indoor heat exchanger 12, the second compressor 16, the second outdoor heat exchanger 14 and the second expansion device 18 are connected by a second refrigerant pipe 19.
The reference numerals 7 and 17 respectively denote direction change valves adapted to change the flow direction of the refrigerant so that the air conditioner can be operated in a cooling or heating mode. The direction change valves 7 and 17 are respectively connected to suction lines 6a and 16a and discharge lines 6b and 16b of the first and second compressors 6 and 16, and controlled by the control unit so that the cooling and heating modes of the air conditioner are selectively established via a single refrigerating cycle of the refrigerant.
Now, the operation of the above-described conventional air conditioner provided with two compressors will be described in detail.
In case that the air conditioner is operated in a cooling mode and a cooling load in a room to be eliminated is large, as shown in FIG. 1, the control unit operates both of the first and second compressors 6 and 16, and a high-temperature and high-pressure refrigerant discharged from the first and second compressors 6 and 16 is transferred to the first and second outdoor heat exchangers 4 and 14. When the refrigerant passes through the first and second outdoor heat exchangers 4 and 14, the refrigerant is heat-exchanged with the peripheral air, thereby being condensed from a high-temperature and high-pressure gaseous state into a high-temperature and high-pressure liquid state. Then, the condensed refrigerant in the high-temperature and high-pressure liquid state is transferred to the first and second expansion devices 8 and 18. When the condensed refrigerant passes through the first and second expansion devices 8 and 18, the refrigerant is expanded into a low-temperature and low-pressure state and then introduced into the first and second indoor heat exchangers 2 and 12. When the expanded refrigerant passes through the first and second indoor heat exchangers 2 and 12, the refrigerant is heat-exchanged with air in the room, thereby absorbing heat and then being evaporated into a gaseous state. Here, the first and second indoor heat exchangers 2 and 12 function as coolers.
In case that the air conditioner is operated in the cooling mode and a cooling load in the room to be eliminated is small, the control unit operates only the first compressor 6. A refrigerant discharged from the first compressor 6 circulates along the first outdoor heat exchanger 4, the first expansion device 8, the first indoor heat exchanger 2 and the first compressor 6. Here, the first indoor heat exchanger 2 functions as a cooler.
On the other hand, in case that the air conditioner is operated in a heating mode and a heating load in the room to be eliminated is large, as shown in FIG. 2, the control unit operates both of the first and second compressors 6 and 16, and a high-temperature and high-pressure refrigerant discharged from the first and second compressors 6 and 16 circulates in the opposite direction of the circulation of the refrigerant in case that the air conditioner is operated in the cooling mode and the cooling load in the room to be eliminated is large. Here, the first and second indoor heat exchangers 2 and 12 function as heaters.
In case that the air conditioner is operated in the heating mode and a heating load in the room to be eliminated is small, the control unit operates only the first compressor 6. A refrigerant discharged from the first compressor 6 circulates along the first indoor heat exchanger 2, the first expansion device 8, the first outdoor heat exchanger 4 and the first compressor 6. Here, the first indoor heat exchanger 2 functions as a heater.
The conventional air conditioner comprising the first and second compressors 6 and 16 copes with only the amount of the cooling or heating load in the room. Since it is difficult for the conventional air conditioner to rapidly cope with the variation of the cooling or heating load, the conventional air conditioner has a limit in improving comfortableness in a room.
In order to rapidly cope with the variation of the cooling or heating load in the room and to improve comfortableness in the room, an air conditioner comprising four compressors has been proposed. In case that the four compressors are simultaneously operated, such an air conditioner comprising four compressors rapidly copes with the variation of the cooling or heating load in the room, thereby improving comfortableness in the room. However, in case that the four compressors are simultaneously operated, the total amount of excessive currents momentarily generated at the respective compressors exceeds the capacity of a power supply unit for supplying power to the four compressors, thus causing the power supply unit to be overloaded, overheated, and thus damaged.
Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a method for operating compressors of an air conditioner, in which a power supply unit is protected when a cooling or heating load in a room is in the highest grade.
In accordance with one aspect of the present invention, the above and other objects can be accomplished by the provision of a method for operating a plurality of compressors of an air conditioner in accordance with a cooling or heating load in a room, comprising the steps of: (a) determining the cooling or heating load in the room; and (b) sequentially operating the plural compressors when it is determined as a result of the step (a) that the cooling or heating load in the room is in the highest grade.
In accordance with a further aspect of the present invention, there is provided a method for operating four compressors of an air conditioner in accordance with a cooling or heating load in a room, comprising the steps of: (a) determining the cooling or heating load in the room; and (b) sequentially operating the four compressors when it is determined as a result of the step (a) that the cooling or heating load in the room is in the highest grade.
In accordance with another aspect of the present invention, there is provided a method for operating first and second compressors respectively having a large capacity and third and fourth compressors respectively having a small capacity in accordance with a cooling or heating load in a room, comprising the steps of: (a) determining the cooling or heating load in the room; and (b) operating the first and second compressors simultaneously, and operating the third and fourth compressors simultaneously after a first set time from the beginning of the simultaneous operation of the first and second compressors, when it is determined as a result of the step (a) that the cooling or heating load in the room is in the highest grade.
In accordance with yet another aspect of the present invention, there is provided a method for operating first and second compressors respectively having a large capacity and third and fourth compressors respectively having a small capacity in accordance with a cooling or heating load in a room, comprising the steps of: (a) determining the cooling or heating load in the room; and (b) operating the first and third compressors simultaneously, and operating the second and fourth compressors simultaneously after a first set time from the beginning of the simultaneous operation of the first and third compressors, when it is determined as a result of the step (a) that the cooling or heating load in the room is in the highest grade.